1. Field of the Invention
The present invention relates to a substance and/or heat exchanging tower.
2. Prior Art
Conventionally, a substance and/or heat exchanging tower such as a distillation tower, an absorption tower and a recovery tower comprises a packing generally composed of sheet-like bases which is used as media for the contact of a liquid and a gas. In addition, other conventional packing of this type has been composed of materials other than sheet-like bases. For example, some packings have been composed of net-like bases instead of sheet-like bases. Though a packing composed of net-like bases exhibits good performance, the price thereof is too high for practical use. In comparison, a packing composed of sheet-like bases is suitable for practical use due to its low price, though it exhibits a slightly inferior performance. Hence, improvement in the performance of a packing employing sheet-like bases is demanded.
It is known that it is necessary to heighten contact efficiency between a liquid and a gas in order to improve the performances of this type of packing. Various means have been attempted therefor. One attempt is to increase the volume of the packing per unit volume of the tower. This intends to increase a gas/liquid contact area by increasing the volume of the packing. However, there occurs one problem in this method. Namely, a larger volume of packing causes a higher pressure loss in the upward gas flow. This has a deleterious effect on the operation of a substance and heat exchanging tower. Even if the contact area is increased, improvement in contact efficiency cannot be accomplished unless sufficient diffusion of the gas and liquid is effected on the surface of the packing.
In practical operation of the tower, since the viscosity and surface tension of the liquid have more influence on the operational conditions of the tower than those of the gas, it is necessary to improve the diffusion of the liquid particularly. Consequently, it has been attempted to improve the efficiency of conventional packing by improving the diffusion of liquid.
Japanese Patent Publication No. 15554/79 of Huber discloses a method of forming channels on the surface of a sheet-like base and thereby diffusing a liquid to the entire surface of the base. However, it is only the spread of the liquid that this method takes into consideration.
Further, in some conventional packings, it is intended to spread a liquid in a lateral (horizontal) direction by providing gatherings on the surface of a sheet-like base horizontally.
In the case of providing gathering or channels on a sheet-like base in order to spread a liquid in horizontal direction, it is more advantageous to effect diffusion of a liquid in horizontal direction that the depth of the fold of gathering or a channel be made larger. However, if the surface of the packing is inclined in a horizontal direction, when the packing is mounted in the tower, the liquid flows to a lower part running down the channel due to the inclination, resulting in a polarized liquid flow. In using this kind of packing, a polarized liquid flow is one of the main problems with respect to the performance of the packing. To overcome this problem, packings are provided in shallow gatherings. However, such a method still does not provide a satisfactory liquid spread.
In order to heighten the contact efficiency between a liquid and a gas, it is necessary not only to accomplish the diffusion of the liquid as explained above but also to improve the mutual relationship of flows of the liquid and the gas, taking the relation between the liquid and the gas into consideration.
One possible method for solving the above problem is to break a boundary film existing on the interface between the liquid phase and the gas phase by providing a specific shape of reliefs on the surface of the sheet-like base. Though it has been known that the breakage of a boundary film is useful for the improvement of contact efficiency, no conventional packing has been found which can accomplish both the diffusion of a liquid and the breakage of a boundary film.
For instance, the packing described in Japanese Patent Publication No. 15554/79 does not include the concept of breaking a boundary film. The method according to Japanese Patent Publication No. 15554/79 is not satisfactory from the viewpoints of both the diffusion of a liquid and the breakage of a boundary film.